can you further explain of what it does?

well,it is just a 3*3 chest with filter,and it does nothing beyond that.

but if you wonder,this is because by have a big container,you will able to share item without design too much about belt layout,
have a chest with filter make you able manage how much resource you want to keep without belts "buffer" too much item in it.

combine both make it super powerful so that some people are using cargo wagon for this kinda functionalities.

so I just make it unlock after circuit network,which is relatively easy to reach in vanilla tech tree(even with space exploration),and make you have reason making mall for combinator before you actually need it.

I do have thinking about make it bigger,my original plan is make a 14*14 container,but I think that will be too op.(like you dont really have reason to make belts and design their path any more

so like warehouse?

so like warehouse?

yes,but you can set filter to manage it without using circuit network!

but downside is this so call "ware house" cannot be blueprint and cannot connect to circuit network,
so if you want to have same functionality without manually setting it,you still need other warehouse mod and designing with combinators.

so it is "Early game Smart Warehouse" I will say..